The present invention relates to the field of electrically conducting contact elements used for the connection of electrical circuits, either in connectors, where they are housed in supports made from an insulating material, or individually by implantation in board circuits, through openings of a suitable diameter. Such contact elements have a general structure formed from a front part whose function is to ensure the electrical contact with another external element, a middle part usually carrying fixing elements such as lugs or hooks, and a rear part, terminal or "contact tail", for connection with the wires or wiring elements of the circuits to be connected.
Due to the increasing industrial tendency to reduce manufacturing costs, manual positioning of the contact elements is being replaced more and more by automatic implantation thereof. The presentation in large quantities the best adapted for supplying the implantation machine is the securing of the contact elements on a continuous strip, most often by their rear end, or contact tail, forming a temporary support from which they are removed at the time of implantation.
A frequent operating method is to form, from the same metal material, the contact elements and the supporting strip to which they are fixed, the separation operation taking place by breaking a previously thinned-down part of the tail by which the contact is fixed to the supporting strip.
The assembly is then in the form of a thin and flexible metal strip, often called "border", on one side of which, arranged like a comb, a plurality of contact elements are fixed by their tail, these elements being punched out. This method of presentation is advantageous in that it allows the contacts to undergo all the manufacturing treatment operations, such as electroplating for example, as well as their storage then their implantation, while keeping them on the supporting border rolled up on a mandrel.
It is by means of the thinned part of the contact tail that, after separation, the contact element is then implanted, either by being mounted in a connecting body, or directly by being mounted in a board circuit.
It is also on this part, square or rectangular in section, that by use of a rotary-end wiring tool, the connection with the cabling wire of the equipment is carried out for example by wrapping.
To minimize the consequences of the geometrical fluctuations of the position of the contacts during these mechanized operations of implantation and wrapping, it is necessary for the contact tail to be pointed, in the shape of a cone or a pyramid, which ensures the automatic correction of positioning errors.
Now this point is created from the part of the tail previously thinned-down for breaking and separation from the supporting strip, and there is a risk of incompatibility between the two functions assumed by this thinned-down part.
In fact, during handling of the strip fitted with its contacts, and in particular during the depositing of a protecting metal layer by electroplating, the thinned-down portion of the tail participates in a first function, that of securing the contact element. It is then highly desirable for the thinning to be limited to a value which retains for this portion a high resistance to bending, so as to avoid at this point any risk of deformation, which may even lead to premature separation of some elements.
On the other hand, the thinned-down portion assumes, after the operation for separating the contact, a second function, that of guide point for mounting and wrapping, which function requires a thinned-down portion having a shape forming a sharp point, in the form of a pyramid with negligible truncation. Now this condition is contradictory to the first one, for it leads to adopting considerable thinning down, with all the drawbacks explained above, whereas, from the first function thereof, it follows that a very moderate value thereof should be adopted which leads, with harmful consequences, after the contact has been detached, to a heavily truncated pyramid-shaped point, totally inadapted to the role of fitting guide, the need for which was shown above.